Conclusions
With the developed assay, C. officinalis can be reliably identified and admixtures of this species as adulterant of saffron can be revealed at low levels.
Results
For this study, five markers (ITS, rbcL, 5' trnK-matK, psbA-trnH, trnL-trnF) of 10 Calendula species were sequenced and analyzed for species-specific mutations. With the application of two developed primer pairs located in the trnK 5' intron and trnL-trnF, C. officinalis could be distinguished from other species of the genus and all outgroup samples tested. Adulterations of Calendula DNA in saffron could be detected down to 0.01%. Conclusions: With the developed assay, C. officinalis can be reliably identified and admixtures of this species as adulterant of saffron can be revealed at low levels.